Hot melt adhesive material metered dispensing systems must be operated intermittently in order to, for example, only deposit the hot melt adhesive material upon predetermined regions of substrates, at predetermined times, so as not to cause operational problems or to result in undesirable product characteristics, and concomitantly, to control the flow of the hot melt adhesive material during those periods of time when the hot melt adhesive material is not actually being dispensed. Control modules, having suitable valve mechanisms incorporated therein, are conventionally used to effectively control the starting and stopping of the flow of the hot melt adhesive material to the dispensing nozzle and its associated discharge orifice. In view of the fact that the metering pumps, for supplying the hot melt adhesive material to the control module, are typically operated in a continuous manner for achieving proper or desirable operational and control parameters, the hot melt adhesive material must therefore be effectively re-routed during those periods of time that the hot melt adhesive material is not actually being conducted to the dispensing nozzle and its discharge orifice. This has been conventionally achieved by means of the control module which is effectively provided with two outlet ports whereby the hot melt adhesive material can alternatively be delivered to the dispensing nozzle and its discharge orifice or to a recirculation passage or circuit. More particularly, the control module conventionally comprises a pair of poppet-type valves disposed internally thereof so as to in fact respectively control the flow of the hot melt adhesive material to the dispensing nozzle and its discharge orifice, or to the recirculation passage or circuit. The two poppet-type valves are usually mounted upon opposite ends of a single stem member, whereby the poppet-type valves and the single stem member effectively form a reciprocally movable spool valve, and accordingly, when the spool valve undergoes its reciprocal movement in a first one of its two opposite directions, a first one of the poppet valves will effectively OPEN a first outlet port leading to the dispensing nozzle and its discharge orifice, while the second one of the poppet valves will simultaneously begin to CLOSE the second outlet port leading to the recirculation passage or circuit, and alternatively, when the spool valve undergoes its reciprocal movement in a second one of its two opposite directions, the second one of the poppet valves will OPEN the second outlet port leading to the recirculation passage or circuit while the first one of the poppet valves will effectively begin to CLOSE the first outlet port leading to the dispensing nozzle and its discharge orifice.
While the aforenoted conventional spool valve structure enables the hot melt adhesive material dispensing system to effectively operate substantially satisfactorily, in reality, the structural design of the conventional spool valve lead to operational problems. More specifically, the spool valve requires a finite amount of time to undergo its reciprocal movements between its two oppositely disposed extreme positions at which, for example, the first one of the poppet valves effectively OPENS the first outlet port leading to the dispensing nozzle and its discharge orifice, while the second one of the poppet valves simultaneously begins to CLOSE the second outlet port leading to the recirculation passage or circuit, and alternatively, when the second one of the poppet valves OPENS the second outlet port leading to the recirculation passage or circuit while the first one of the poppet valves effectively begins to CLOSE the first outlet port leading to the dispensing nozzle and its discharge orifice. Accordingly, while the spool valve is effectively in motion, that is, while the spool valve is moving between its oppositely disposed extreme positions, both of the poppet valves are effectively removed from their respective valve seats whereby both the first and second outlet ports, respectively leading to the dispensing nozzle and its discharge orifice, and to the hot melt adhesive material recirculation passage or circuit, are at least partially OPEN and therefore effectively fluidically communicate or “cross-talk” with each other. Accordingly, still further, the desired or proper dispensing of the hot melt adhesive material is not always properly, accurately, or completely ensured or achieved.
A need therefore exists in the art for a new and improved spool valve and valve seat assembly, for use within a control module of a hot melt adhesive material dispensing system, wherein the new and improved spool valve and valve seat assembly of the control module will be structured so as to effectively prevent fluid communication or “cross-talk” between the first outlet port, leading to the hot melt adhesive material dispensing nozzle and its discharge port, and the second outlet port, leading to the hot melt adhesive material recirculation passage or circuit, during those periods when the control module is effectively reciprocally cycling the spool valve between its oppositely disposed extreme conditions for alternatively permitting the hot melt adhesive material to be dispensed from the first outlet port leading to the hot melt adhesive material dispensing nozzle and its discharge orifice, or for re-routing the hot melt adhesive material through the hot melt adhesive material recirculation passage or circuit so as to prevent the hot melt adhesive material from being dispensed from the first outlet port leading to the hot melt adhesive material dispensing nozzle and its discharge orifice.